Not Applicable
Not Applicable
1. Field of the Invention
This invention relates to disk drive suspensions, the very small springs that carry read/write heads in a slider in close proximity to a disk. These suspensions comprise a load beam or rigid portion, a spring portion and a flexure comprising a frame support and a cantilevered tongue portion that serves to carry the slider for gimballing motion about a load point called a dimple. The flexure tongue, and slider, extends at an angle to the disk termed the pitch static attitude (PSA) that varies with the vertical extent or height of the dimple. PSA is the angle between flexure tongue (or slider disk side surface) and the disk surface before touch down of the suspension onto the rotating disk. (Referencexe2x80x94FIG. 1) More particularly, the invention relates to optimization of suspension design to minimize flexure pitch static attitude changes responsive to variations in dimple height.
2. Description of the Related Art
Many designs of flexures have been developed over the years in an effort to achieve an optimum combination of stiffness in pitch, roll, and sway (lateral) directions appropriate to the application at hand. An application may require certain suspension size, angles, preload, slider characteristics, space, limiters, and other features be considered, alone and in combination. See U.S. Pat. Nos. 5,008,768, 5,138,507, and 4,829,395 as illustrative. In all of these designs, the manufacturer of the suspension achieves a desired pitch static attitude by a combination of dimple height adjustment and flexure rail offset. This has typically been a cut and try effort by the toolmaker to get a forming die adjustment as needed for the finished product. If a change in suspension offset height is necessary (because of a specification change from the customer, for example) the process must be redone, again by cut and try methods.
It is an object of the invention to provide a method of design and a further object to provide a design of disk drive suspension in which the PSA varies little with a change in dimple height owing to the precise placement of the dimple contact point taking into account the various geometric givens of the particular suspension.
These and other objects of the invention to become apparent hereinafter, are realized in a method of designing a load beam assembly flexure, including locating the dimple contact point according to the formula
I1/I2=(b+c)2/b2
where
I1xe2x80x94moment of inertia of flexure tongue (excluding outrigger portion);
I2xe2x80x94moment of inertia of the flexure outrigger (excluding tongue portion);
bxe2x80x94length from dimple contact point to edge of the flexure offset rail;
cxe2x80x94length from dimple contact point to welding point,
and preferably such that the change in pitch static attitude with a change in dimple height is less than 3 minutes of pitch static angle per 0.001xe2x80x3 of dimple height.
The invention apparatus includes a disk drive suspension having a rigid portion and a flexure comprising a frame supported on said rigid portion at a support point, and a tongue cantilevered between frame outriggers and from the frame in offset relation, the tongue having a free end for carrying a slider in gimballing relation in operative proximity to a disk, the tongue free end being angularly displaced from the rigid portion at a dimple contact point corresponding to a predetermined suspension pitch static attitude angle, the contact point being located on the tongue according to the formula:
I1/I2=(b+c)2/b2
where
I1 is the moment of inertia of the flexure tongue (excluding the outrigger portion)
I2 is the moment of inertia of the flexure outrigger (excluding the tongue portion)
b is the length between the dimple contact point and the edge of the flexure offset and,
c is the length between the dimple contact point and the support point,
whereby said suspension is substantially free of change in pitch static attitude angle through variations in the vertical displacement of said dimple contact point.
The invention apparatus further includes a disk drive suspension having a load beam with a rigid portion and a flexure comprising a frame attached to the load beam rigid portion at a welding point, the frame comprising left and right outriggers and a tongue between the outriggers and cantilevered from the frame at a flexure offset rail, the tongue having a free end for carrying a slider in gimballing relation in operative proximity to a disk, the tongue free end being angularly displaced from the load beam by a dimple at a dimple contact point corresponding to a predetermined suspension pitch static attitude angle, the dimple contact point being located on said tongue according to the formula above, whereby the suspension is substantially free of change in pitch static attitude angle through variations in the vertical height of the dimple and corresponding vertical displacement of the dimple contact point.
In previous designs the manufacturer has been unable to control pitch attitude independently of dimple size and off set height. Thus, a variation in dimple height that might be required for other design reasons becomes an unwanted variation in pitch static attitude. Similarly, variations in flexure rail height also vary the PSA. This invention provides a suspension design and method to control PSA by the geometry of the flexure independently of the dimple size or the flexure rail offset, so that the desired PSA is designed in and not a problem for the toolmaker.
In the invention, the inertia of the outrigger and the tongue, and the position of the dimple and welding spot where the flexure is attached are used for PSA control. Using only these characteristics, a suspension designer can control PSA independently of other variables and, particularly importantly, independent of dimple height and variations in dimple height. In general, this is possible by determining in accordance with a formula provided herein an ideal location on the tongue for dimple location or engagement that is varied by varying the geometry of the outrigger, tongue and other geometrical features that are more readily adjustable during the design process. Thus, unlike existing production process adjustment of PSA, which is costly and subjected to random, if not frequent, mistakes by the individual operator, the invention method of designing PSA control into the suspension is low cost and repeatable without random errors or operator mistakes, for a substantial saving in manufacturing time and cost and increased efficiency.
With the invention, once the design is set the PSA does not need to be adjusted, despite a dimple size or height change for whatever reason, for a given flexure geometry, including location of welding spot and dimple gimbal location.